In processes for fabricating integrated circuits, different semiconductor devices need to be connected to form circuits after forming semiconductor device structures. As the integration circuits develop, requirements on integration levels and on performances of the integrated circuits become higher and higher. To improve the integration levels and reduce costs, critical dimensions of the semiconductor devices continuously decrease and circuit densities in the integration circuits continuously increase. Correspondingly, a wafer may not provide enough area to form interconnecting wires for conventional circuits.
To meet the requirements for interconnecting wires due to the reduced critical dimensions, interconnecting structures are used to connect between different metal layers and to connect metal layers with the semiconductor structures. The interconnecting structures usually include interconnecting wires and conductive plugs in contact holes. The conductive plug in the contact hole may be used to connect to a semiconductor device. The interconnecting wires may be used to connect conductive plugs in different semiconductor devices, to form circuits.
As process nodes of the integrated circuits and the critical dimensions of the devices continuously decrease, contact areas of the conductive plugs in the contact holes continuously decrease, and a contact resistance between the conductive plugs and the semiconductor devices increase. The formed semiconductor structures have poor performances.